Using Model Theory for Architecture Definition in Complex System Design

Architecture Definition, which is central to system design, is one of the two most used technical processes in the practice of model based systems engineering. In this paper a fundamental approach to architecture definition is presented and demonstrated. The success of its application to engineering problems depends on a precise but practical definition of the term architecture. In the standard for Architecture Description, ISO/IEC/IEEE 42010:2011, a definition was adopted that has been subsumed into later standards. In 2018 the working group JTC1/SC7/WG42 on System Architecture began a review of the standard, holding sessions late in the year. This paper extends and complements a position paper submitted during the meetings, in which Tarski model theory in conjunction with ISO/IEC 24707:2018 (logic-based languages) was used to better understand relationships between system models and concepts related to architecture. Definitions of architecture and system are now offered independent of the working group that have a mathematical foundation but are stated in simple intuitive terms. The nature of the definitions supports a fundamental expression of architecture definition that can be applied throughout the system lifecycle. The engineering utility and benefits to complex system design are demonstrated in a diesel engine emissions reduction case study.